If you truly don't want to be racist, you first accept that you are, and interrogate the ways that your words and behaviors (and existence) contribute to the devaluing of black lives and experiences. And then BE BETTER. I am not suggesting that we accept racism. I am saying that we need to accept that it exists in us (as individuals) in order to eradicate it.
I see so many examples of conversations on facebook that end with: "you called me a racist, I'm unfriending you."
That CANNOT be the reaction to someone calling you racist. Our society is inherently racist. We've all been inculcated with racist propaganda and stereotypes, and those of us who are white have benefited from a society designed for us. We've seen countless examples in the training. We are racist, as a people and as white individuals. Whoever called you out is right, and they are giving you the chance to learn and grow.
Accepting that you are racist sucks. Growth is uncomfortable. Get over it. The only way you can fix a problem is if you acknowledge that there is one.